1. Field of the Invention
The present invention pertains to an operating device for thread guide rails in crochet galloon looms, of the type comprising at least a drive lever having one end pivoted on a fixed structure and a second end connected to a thread guide rail, at least an eccentric connected to the drive lever through a connecting rod and actuating means acting on the eccentric in order to impart the thread guide rail an alternate longitudinal movement.
The device is particularly adapted to be used in place of conventional weft-making devices in crochet galloon looms and the like.
2. Prior Art
It is known that in crochet galloon looms designed to produce bands, laces and the like the thread guide rail is generally operated so that it carries out an oscillatory motion in order to cause each threading tube mounted thereon to perform a substantially semielliptical trajectory on either side of a plurality of needles disposed in a mutual side by side relationship and lying in a horizontal plane. To this end the thread guide rail is submitted to the action of a lifter device imparting it an oscillatory motion in a vertical direction in combination with the action of a weft-making device imparting said thread guide rail a horizontal oscillatory motion in a longitudinal direction.
Both the lifter device and the weft-making device cause the operation of the thread guide rail through eccentrics provided with a continuous rotatory motion and connected to the thread guide rail by means of suitable linkages. The weft-making device is usually provided with appropriate means for suitably regulating the horizontal stroke of the thread guide rail in order to determine, depending upon the width of the lace band to be manufactured, the number of needles included within the trajectory traced by each thread guide rail.
The weft-making devices currently used are adapted to allow the horizontal translations of the thread guide rail to start, at the beginning of each forward and backward stroke thereof, at the same instant in which the lifter device begins raising the thread guide rail itself.
As a result, the threading tubes are subjected to carry out horizontal translations when their lower ends are still disposed below the lying plane of the needles and are about to be raised with respect to the needles under the action of the lifter device.
Under this situation, in order to avoid any interference between threading tubes and needles, it is necessary to make the thread guide rail strokes longer than the width of the band or lace being worked.
By this contrivance the lifter device can sufficiently raise the threading tubes before the latter, during their horizontal translation, may hit on the needles.
The increase of the horizontal strokes of the thread guide rail, and as a result of the threading tubes, involves the necessity to remove the needles located adjacent the opposed sides of the produced bands from the loom, that is to remove the needles in the regions where the movement reversal of the threading tubes occurs. Obviously, due to this situation, one portion of the whole loom length cannot be exploited for the purpose of producing manufactured products, since this portion must be left clear of needles in order to enable the movements of the thread guide rails.
Moreover in this case there is also another drawback in that it is necessary to thoroughly change the needle distribution along the loom each time the type and/or sizes of the bands or laces being worked have to be modified. Said operations, which are carried out manually, remarkably increase the working idle time necessary to set up the machine.
A further drawback of the known art is due to the fact that along the loom it is necessary to arrange members adapted to recover the excess weft yarns drawn out by the threading tubes during the idle strokes.